After Udo Dirkschneider left Accept in 1987, a large fan community followed him to U.D.O.

Starting with the first two albums Animal House in 1987 and Mean Machine in 1988, U.D.O. proved to be pure heavy metal without any Trend-Sound influences. Both albums continued where Accept had left off in 1986 with Russian Roulette. Apart from U.D.O., Animal House was recorded by Peter Szigeti (guitars), Frank Rittel from Warlock on (bass), Mathias Dieth from Sinner and Gravestone (guitars) and Thomas Franke (drums).

From 1992 to 1996, Accept reformed their classic line up and Dirkschneider put U.D.O. on hiatus to record three albums with his old bandmates. After another break-up, Dirkschneider returned to U.D.O. with Stefan Kaufmann (guitar), Jürgen Graf (guitars), Fitty Wienhold (bass) and Stefan Schwarzmann (drums). Udo Dirkschneider and Stefan Kaufmann then recorded tracks for the Tribute to Judas Priest compilation of Judas Priest cover songs, performing the track "Metal Gods".

1997 saw the release of Solid, the first full-length U.D.O. album to feature the guitar work of Stefan Kaufmann. It was featured on the Rock Hard magazine reader charts for more than a year after its release.

The album was followed up with No Limits in 1998 and featured a similar songwriting approach as the previous year's effort. It also featured U.D.O.'s first returning lineup since the band's inception ten years prior. The album also featured a cover of the Austrian pop band Supermax's hit single "Love Machine".

In 1999, the band released the critically acclaimed Holy, which was a return to the guitar-driven sound similar to the Balls to the Wall-era Accept. A world tour followed with dates in the United States and several other major countries. Lineup changes occurred during the second part of the tour with Igor Gianola of Gotthard, replaced Jürgen Graf. When the No Limits tour concluded, Stefan Schwarzmann quit the band. On the 2000 leg of the Holy tour, Lorenzo Milani was the new drummer. The tour also spawned U.D.O.'s first live album, Live from Russia, a two-disc affair which featured many of the classic Accept tunes (with the exception of "Balls to the Wall") that have since become staples of U.D.O.'s set.

2002's Man and Machine received a somewhat lukewarm response. Despite standout songs like the title track and "Private Eye", the album was ultimately less successful than its predecessor. It is notable for spawning a promo video of "Dancing With An Angel", featuring a duet between Udo and Doro Pesch of Warlock.

The next two studio releases, 2004's Thunderball and 2005's Mission No. X, were slightly livelier affairs, with the band's touring of Germany, South America, and Eastern Europe. Sonically, the former shared much in common with Timebomb, while the latter followed No Limits.

It was with 2007's Mastercutor that saw U.D.O. return to form. The album was the most financially successful in years and received universally high marks from musical critics and metal fans alike. Udo's appearance on Finnish metal band Lordi's 2006 album, The Arockalypse, exposed U.D.O. to a wider audience.

U.D.O.'s twelfth studio album, Dominator, was released on 21 August 2009. U.D.O.'s next studio album, Rev-Raptor was released on 20 May 2011.

In September 2012, Stefan Kaufmann, longtime guitar player in U.D.O., left the band for health reasons. He continues to work in the surroundings of the band and produces for other bands in his own ROXX studio. In early 2013, guitarist Igor Gianola left the band "due to conflicts between band appointments and his private life and business." They were both replaced by Andrey Smirnov and Kasperi Heikkinen.

In late 2014, drummer Francesco Jovino left the band for personal reasons. He went on to join fellow German power metal band Primal Fear. His replacement was Udo Dirkschneider's son, Sven.

U.D.O. released the fifteenth studio album Decadent on 23 January 2015.

In October 2016, the band released an Accept only live album titled Live - Back to the Roots, under the name Dirkschneider, which was Udo Dirskchneider's final send-off of ever performing any Accept song again. They will continue to tour as Dirkschneider into 2017.